public SymbolAndPower(string symbol, int power)
{
Ensure.NotNullOrEmpty(symbol, nameof(symbol));
Ensure.LessThan(power, 5, nameof(power));
Ensure.GreaterThan(power, -5, nameof(power));
// not sure about throwing here but I think it means something is wrong more often.
this.Symbol = symbol;
this.Power = power;
}